Field of the Invention
The present invention relates to a technique for performing a liquid treatment to a substrate by supplying a treatment liquid to the substrate while rotating the substrate.
Background Art
Semiconductor fabrication processes include a step of forming a circuit pattern on a surface of a substrate such as a semiconductor wafer using photolithography. When dry etching is performed using a photoresist as an etch mask, reaction products called polymer is unavoidably adhered to the surface of the substrate. The polymers are removed in the next step.
The polymer removing process is performed by supplying a polymer removing liquid to the central portion of the substrate while rotating the substrate about a vertical axis. The polymer removing liquid is supplied under heated condition for enhanced reactivity. The substrate draws heat from the polymer removing liquid as it flows from the central portion to the peripheral portion of the substrate, so that the temperature of the polymer removing liquid lowers. The peripheral portion of the substrate is likely to be cooled because of the high circumferential speed thereof. Thus, the time required to remove the polymer at the peripheral portion of the substrate is longer than the central portion.
In order to achieve in-plane uniformity of the thermal condition, a scan discharge method is sometimes used. The scan discharge method moves a nozzle discharging the polymer removing liquid such that the falling point of the polymer removing liquid onto the substrate is moved between the central portion and the peripheral portion of the substrate. However, during the scan discharging, when the nozzle is positioned above the peripheral portion of the substrate, the polymer removing liquid covering the central portion of the substrate may be lost so that the central portion of the substrate is exposed to the substrate surrounding atmosphere (air atmosphere). This may results in generation of particles on the surface of the substrate.
Japanese Patent Laid-Open Publication No. 2007-088381A (Document 1) discloses a substrate liquid treatment apparatus having two nozzles mounted to one nozzle arm. The two nozzles moves along a circular arc passing through the center of the substrate in a plan view, by swinging the nozzle arm. The two nozzles mounted to the nozzle arm with the nozzles being separated at a distance of about one third of the diameter of the substrate. Document 1 recites that, by moving the arm while concurrently discharging the treatment liquid from the two nozzles, the whole surface of the substrate can be treated uniformly and the central portion of the substrate is prevented from being exposed to the substrate surrounding atmosphere.
However, in the apparatus of Document 1, the treatment liquid discharged from one nozzle located near the peripheral portion may disturb the flow of the treatment liquid having been discharged from the other nozzle located near the central portion and flowing toward the peripheral portion of the substrate. Under such a situation, substances having been removed from the substrate by the treatment liquid and flowing toward the peripheral portion of the substrate may be returned toward the central portion of the substrate, or may stagnate, so that the substances are not likely to flow out of the substrate and are likely to adhere to the substrate again.